Responding to the Investigatory Powers Tribunal’s ruling against GCHQ today, she said: “The most serious problem with GCHQ's intelligence sharing regime with the USA was the fact that it was carried out without sufficient democratic oversight.

“Today's IPT judgement recognises this, stating that the lack of transparency around the arrangement was unlawful.

“A great deal of emphasis has been put on the apparent threat to privacy of GCHQ and the NSA's actions. This judgement rightly re-focuses concerns on the threat to democratic legitimacy.”